Detent mechanism for recoil operated firearms



July 31, 1951 B. MAILLARD DETENT MECHANISNI FOR RECOIL OPERATED FIREARMSFiled Feb. 15, 1948 @N N@ wh@ L nl L J .n /g/ n ATTORNEY Patented July31, 1951 UNITED STATES 'PATENT'fMorFCE nErEN'r MEcnANlsM Fon macon.

opnamen rmnARMs Bernard Maillard, Genevaswitzerlend, assigner to BrevetsAero-Mecaniques S. A., Geneva, Switzerland, a society of SwitzerlandApplication February 13, 1948, serial No. 8,174 In Luxemburg February24, 1947 7 claims. (c1. ia-fes) The present invention relates to releaseor detent mechanisms, i. e. mechanisms for temporarily holding a movablepart'against the action of a high return force, and it is moreespecially but no exclusively concerned with breech recoil operatediirearms, that is to say either semiautomatic rearms, with which thegunner is to operate the trigger on every shot, or automatic arms firingby brusts and, of course, mixed operation arms capable either ofworking'in semi-automatic or in fully automatic fashion.

Its object is to provide a mechanism of this kind which is betteradapted to meet the requirements of practice than those used 'up to thistime.

According to a feature of my invention, in order to reduce the violenceof the shock due to the locking engagement of the movable part with thedetent or catch means, I divide the mass of said means into at least twoportions arranged and mounted in such manner as to be brought intomotion successively in the course of said engagement with the movablepart, whereby the force of inertia which opposes the living force ofsaid part at the beginning of this engagement is only a portion of thetotal inertia forces brought into play for fully stopping said movablepart.

According to another feature, in a system of the kind in questionincluding at least one detent system capable, under the eiiect of theshock resulting from its engagement with the movable part, of undergoinga certain displacement against the action of elastic return means, Iarrange said detent system to cooperate with a unidirectional shockabsorbing device adapted to brake the motion due to this engagement,whereby said return means is relieved from most of the shock absorbingstresses and need, consequently, be only capable of overcoming theforces that oppose the return of the detent system and the movable partto the position that these elements occupied when they engaged eachother.

Preferred embodiments of my invention will be hereinafter described withreference tothe accompanying drawings, given merely by way of exampleand in which:

Figs. 1 and 2 diagrammatically show, respectively in elevation and inplan View, withvparts in section, a detent mechanism according to thepresent invention; Y

Fig. 3 shows in elevational section a modilcation of some elements ofthis system.V

The invention will now' be described with reference to a breech recoiloperated lfirearm includ-'- ing, among other parts, afbreech casing -Iin which Ais mounted a movable breech 2 subjected to the action of areturn spring (not shown) exerting thereon a high return force in thedirection of arrow F (Figl).

Generally speaking, the detent mechanism is 'made in the usual manner,including for instance a sear 3 adapted to come, under the action lof aspring 4, across the path of travel of` a projection or nose 5 carriedby breech '2, a trigger 3a being provided for disengaging scar 3 fromprojection 5 when it is desired to nre a shot.

lIt has alreadybeen proposed, in order to re duce the shockresultingfrom the initial engagement of the breech (moving incounter-recoil direction) with the sear,tomo unt the sear 'properpivotally on a 'support slidable, in a direction parallel to thedirection-of movement of the breech, against theraction of a springplaying both the part of shock absorber and of return device for themovable elements (scar and slidable support) of the detent unit.

Thus, instantaneous stopping `oi the breech upon its engaging the scarwas avoided and the living force of said breechlwas absorbed during thef braking displacement, of nonenegligible length,Y ofthe movableelements of the detent unit. Y 1

However, th'e'whole of the sliding masses (scar and support) of thisdetent unit was urged in the frontward direction as lsoon as the breechengaged the sear, and thel violence 4of the initial shock was thegreater asthe total inertia of said sliding unit was itself moreimportant.

According to my invention, the violence of the shock in question isfurther reduced by dividing the mass of the-'sliding detent unit into atleast two portions, to' wit the sear 3 proper on the one hand and asliding block ii acting as a support `for said sear, on the other hand,these portions being 'arrangedand mounted in such manner asito besuccessively 'brought into ino'tion as breech 2 cooperates with soar 3.

In this Way, theinertia force which opposes the living force of saidbreech at the beginning of this locking operation, 'to wit, the force ofinertia of sear' 3, Willbe only a fraction, which may be made relativelysmall, of the forcesV of inertia of the whole detent unit.

p Preferably, the" relative'movement of sear 3 with respect to `block G,when engaged by the breech, takes place in a direction parallel to themovement of Said breech. For instance I provide in said'sear anovalfshaped oriiice 1 through which extends a pivot pin 8 mountedbetween two rearward projections 6 of block 6. K.

f' T-it the detent unitwith e. shock absorbing sear 3 first starts saidsear into movement andVv block 6 is moved only afterwards. c

It should be noted that elastic means, land -Il'I will be preferablychosen so as to be stronger than the breech return spring,'so that, oncethe locking engagement shock is absorbed, the whole f i, Y

sliding unit 6, 3 and breech 2 into the position corresponding to thebeginning of the locking engagement.

Taking this fact into account, it may be advantageous, according to acomplementary fea- ;tur'e of my invention which may, eventually, be

applied independently, to provide, in operative connection with/thesliding detent unit, a shock absorbing device which works chiefly duringthe counter-recoil movement of said unit. This shock absorbing device,for instance of the hydraulic type, `may be constructed to absorb by ofthe detent unit and breech 2 is brought' back into the position forwhich projection came into contact with sear 3.

Elastic means 9 might work only during the first portion of the shockabsorbing operation (in which case it should be interposed directlybetween sear 3 and block 6 and be of a strength lower :than that ofelastic means I0 so that the latter will be compressed, as desired, onlyafter `of vsaid shock absorbing operation, that is to say when elasticmeans I0 cornes in turn into action Ato brake-the movement of breech 2.

For this purpose, advantageously, elastic means 9 and I0 will bearranged to bear, through one of their ends, upon breech casing I andthrough their other end, upon sear 3 (concerning means 9) or sear block6 (concerning means I0) i1 Such a solution is illustrated by Figs. land2. Elastic means 9 is comprised of a helical spring housed in a bore 6aextending through sear block 6 along the longitudinal axis thereof, saidspring bearing, through the intermediate of push pieces 1;

II and I2, respectively upon breech casing I and sear 3, so as to urgeit away from said blockG.

Elastic means I0 is then comprised of two helical springs mounted in twohousings 6b provided on either side of bore 6a and closed on the side of:i:

While the arm is ring, sear 3 is kept lowered by control member 3a. Assoon'as this control member is released, the nose of sear 3 comes acrossthe path of travel of projection 5 of the breech and locking takes placeat the beginning of the next counter-recoil stroke of breech 2. Sear 3then moves in the counter-recoil direction, under the effect of theshock, compressingl spring 9. Once it has moved the distance permittedby .oval-shaped orice 1, sear 3 is applied against sear block 6, anddrives it in the frontward direction against the combined actions ofsprings 9 and III. Block 6 then comes into contact with liber plate I4.The kinetic energy Yofthe breech is fully absorbed and sliding unit V6,3 comes back to its initial position under the action lof said springs,driving, in this backward movement, breech 2 against the action of itsreturn spring.

It will be noted that the kinetic energy'ito be absorbed for-stoppingbreech 2 is much higher than the energy to be supplied for bringingbackitself most of the kinetic energy of breech 2, thus correspondinglyrelieving springs 9 and Ill, the

function of which can then be limited substanf- .tially Vto thereturning into position of the detent unit and the breech, which permitsof reducing their'strength to the value just necessary for overcomingthe resistance of the breech return .,-Forthis purpose, I may,advantageously, in

the case of a'detent system made as above indicated, substitute for atleast one of springs IU, a hydraulic brake which is, for instance,constituted as follows (Fig. 3)

I fit, in the corresponding housing 6b, which Yis closed at the front bya guide plug, a'piston I5 ,(playing the part of a push-piece) againstthe `rear face of which bears a return spring I6, the rod I5o of thispiston bearing itself, through its front end, upon breech casing Ithrough the intermediate of fiber plate I4.

- I provide, in piston I5, passages I5a the rear end of which isnormally closed by a valve I1 kept applied against said piston by aspring I8 bearing against an abutment I9 'provided' for this purpose onthe rear end of rod |50. 1 The operation of such a brake is as follows:When sear 3 comes to bear against block 6 and starts driving it incounter-recoil direction, piston I5 compresses Vthe oil and air presentin the rear chamber of housing 6b and eXpels these fluids .which thenpass, through the small sec- `.tions of .flow left between said pistonand the wall of housing 6b, into the front chamber of said housing; thisstroke4 is the shock absorbing stroke proper. Once the kinetic energy of Vbreech 2VV has beenabsorbed, springl, which had been compressedduring the shock absorbing stroke, urges the sliding system and saidbreech in the rearward direction; the-pressure then existing in Vthefront chamber of housing 5b compels valve IIrto move away from its seatand oil `can freely ,flow from the front face to the rear face of pistonI5, this movement taking place vwithou much consumption of energy. .Y Ofcourse the sliding detent unit might be di- .vided into more than twoportions coacting together through the ,intermediate of elastic systemsVsuccessivelybrought into play. Y

"In a generalv manner, .while I have, in the above description,disclosed what I deem to be practical and efcient embodimentsV of vmyinventioniit'should be well understood that I do not Wish to be limitedthereto asV there might be changes made in the arrangement, dispositionandrform of the parts without departing from the principle of thepresent invention as comprehended within the scope of the accompanyingclaims.

Whatlclaimisz Y 1.

l. In combination,'a breech casing, a breech slidable in said breechcasing withV a recoil'and counter-recoil reciprocating motion,saidbreech 99mg .elastically urged in the counter-recoil direction, a detentunit movable in said breech casing including at least one block slidablyguided in said casing in a direction at least substantially parallel tothe direction of movement of said breech and a sear movablyinterconnected with said block to be movable both transversely to saiddirection of movement, so as to engage said breech for stopping thecounter-recoil movement thereof, and with a lost motion, in saiddirection of movement, the mass of said block constituting a substantialportion of the total mass of said detent unit, and means for limitingthe motion of said block in the counter recoil direction.

2. In combination, a breech casing, a breech slidable in said breechcasing with a recoil and counter-recoil reciprocating motion, saidbreech being elastically urged in the counter-recoil direction, a detentunit movable in said breech casing including at least one block slidablyguided in said casing in a direction at least substantially parallel tothe direction of movement of said breech and a sear, means for movablyinterconnecting said sear with said block to make said sear movabletransversely to said direction of movement so that it can engage saidbreech for stopping the counter-recoil movement thereof, saidinterconnecting means being arranged to provide a lost motion in saiddirection of movement, the mass of said block constituting a substantialportion of the total mass of said detent unit, and means for limitingthe motion or said block in the counter-recoil direction.

3. A combination according to claim l in which i the mass of said searis substantially smaller than that of said block.

4. A combination according to claim 1 further including a plate of berinterposed between said block and said breech casing.

5. In combination, a breech casing, a breech slidable in said breechcasing with a recoil and counter-recoil reciprocating motion, saidbreech being elastically urged in the counter-recoil direction, a detentunit movable in said breech casing including at least one block slidablyguided in said casing in a direction at least substantialltT parallel tothe direction of movement of said breech and a sear adapted to engagesaid breech for stopping the counter-recoil movement thereof, pin andslot interconnecting means between said block and sear the slot,provided in one of said two last mentioned parts. extending in saiddirection of movement and the pin. carried inthe other of said twoparts, being of circular cross section and of a diameter equal to thewidth of said slot, whereby said sear is able both to pivot on saidblock transversely to said direction of movement and to slide withrespect to said block in said d1- rection of movement, the mass of saidblock constituting a substantial portion of the total mass of saiddetent unit. and means for limiting the motion of said block in thecounterrecoil direction.

6. In combination, a breech casing, a breech slidable in said breechcasing with a recoil and counter-recoil reciprocating motion, saidbreech being elastically urged in the counter-recoil direction, a detentunit movable in said breech casing including at least one block slidablyguided in said casing in a direction at least substantially parallel tothe direction of movement of said breech and a Sear movablyinterconnected with said block to be movable both transversely to saiddirection of movement, so as to engage said breech for stopping thecounterrecoil movement thereof, and with a lost motion, in saiddirection of movement, the mass of said block constituting a substantialportion of the total mass of said detent unit, means for limiting themotion of said block in the counter-recoil direction, and elastic meansfor urging said detent unit in recoil direction.

'7. In combination, a breech casing, a breech slidable in said breechcasing with a recoil and counter-recoil reciprocating motion, saidbreech being elastically urged in the counter-recoil direction, a detentunit movable in said breech casing including at least one block slidablyguided in said casing in a direction at least substantially parallel tothe direction of movement of said breech and a sear movablyinterconnected with said block to be movable both transversely to saiddirection of movement, so as to engage said breech for stopping thecounter-recoil movement thereof, and with a lost motion, in saiddirection of movement, the mass of said block constituting a substantialportion of the total mass of said detent unit, means for limiting themotion of said block in the counterrecoil direction, unidirectionalshock absorbing means for braking counter-recoil displacements of saiddetent unit with respect to said breech casing, and elastic means forreturning said detent unit and breech in the recoil direction withrespect to said breech casing.

BERNARD MAILLARD.

REFERENCES CITED UNITED STATES PATiizNTs Name Date Birkigt Nov. 14, 1939Number

